Sound-transmitting instrument



l March 30,1926. 1,578,336

A. MARR SOUND TRANSMITTING yIXJSIIRLIIJEHQT Filed' April 5, 1921 of@ae/'lures im] less l/Ian area of queria/re. B.

Ing/entor; Mdm/7,1m

Patented Mar. dit, 1925.

l.,578,33ti

UNlTED PATENT QEFECE.

ALEXANDER MARR., OF MANCHESTER, ENGLAND.

SOUND-TBANS'MITTNG NS'EVUMENT.

Application filed April 5,

To tZ fr0/ionil t may forzati/'fi yBe it known that l, ALEXANDERfiltran, a subject of the King of Great Britain and Ireland,and aresident of li/laiichester, in the county of Lancaster, England, haveinvented certain new and useful improvements in or Relating toSound-Transmitting Instruments, of which the following a speci-.p ftion.

This invention relates to sound transmitting instruments such as e. g.telephone transmitters or microphones, grainopheue record producers,dictating machines, ear trumpets and the like, of the kind wherein themouthpiece or part whereby the sound waves are led to the diaphragm orequivalent of the instrument or the ear, is in the form of aconcentrator chamber having a constricted aperture for the entrance ofthe sound waves.

The object of the invention is to provide an improved arrangement ofconeentrator mouthpiece or the like whereby the sound waves enteringsaine are conveyed in greater amplitude to the diaphragm or equivalentor the tympaiium of the ear with corresponding greater clearness insound reproduction.

According to the invention, there is provided in the concentratormouthpiece or the like at or about the point of greatest width apartition and the sound waves entering the constricted inlet apertureare compelled to pass said partition by a passage or a plurality ofpassages arranged outside of or beyond the periphery of the constrictedinlet aperture, and area or the collective area of which is not lessthan the area of said aperture. Further, according to this invention, Imay in some cases provide the concentrator mouthpiece or the like with atapered or coned exit, or fit in or at the exit thereof a hollowtruncated cone having its smaller ear or apex directed rearwardly, andsaid tapered or coned exit or cone may in some cases be surrounded by anannular space.

In the accompanying drawing, Fig. l is' a section of one embodiment ofthe invention in a telephone transmitter, the exit of the mouthpiece ofwhich is at right angles to the inlet thereof, and Fig. Q is a plan ofFig. 1 with one half of the concentrator ofthe mouthpiece cut away`.Fig. 3 is a section illustrating an embodiment of the invention in thepresent standard 1921. Serial No. 458,810.

mouthpiece for telephone transmitters, dictating machines and othersound transmitting instruments. Figs. i and 5 are fragmentary sections`illustrating modifications of the embodiment shown in Fig. 3. Figs. Gand 7 are fragmentary views partly in elevation and partly in section ofthe exit end of a sound :fave ceneentrator for use with the ear. Fig. 8is a fragmentary section showing a modilication of the enit end of theconcentrator mouthpiece illustrated in Fig. l, ln the drawings and thefollowing' description, like characters of reference indicate likeparts.

Referring first to Fig. l, 2 is the mouthpiece of the transmitter, 3 thediaphragm, l the resistance varying cell and 5 the casing enclosing thediaphragm and cell.

To the inlet of the mouthpiece 2 is lit-ted a concentrator cap 6 dishedor concaved on its inner face 7 and provided with a constricted aperture8 for the lerjtrance of sound waves. Between the cap 6 and themouthpiece 2, i. e., at the widest part of the concentrator chamberconstituted by the mouthpiece and cap, l arrange a partition 9 of metal,vulcanite or other appropriate inaterial, provided with perforations 10.The latter are arranged near the periphery of the partition so that theydo not lie in line with the entrance aperture S hut lie outside orbeyond the periphery of such aperture. rhe perforations 10 are such innumber and size that their collective area is not less than the area ofthe aperture 8. The arrangement is preferably also such that the area ofthe aperture 8 is approximately one fourth of the area of the widestpart of the concentrator chamber whereat the partition 9 is arranged;the distance of the aperture 8 from the partition is approximately onefourth of the diameter of the latter; and the radius of the wall of thedished underside of the cap G is approximately equal to the distance ofthe aperture S from the partition.

rl`he exit of the coiicentrator mouthpiece, which is at right angles tothe inlet thereto, is fitted in a ferrule l1 or equivalent on 0il in thecasing 5 so that it lies close to the diaphragm 3. `Within the exit endof the coueeutrator mouthpiece is fitted a hollow truncated cone l2 ofmetal. vulcanite or other appropriate material having itsapex orsmall``1 end opening to the diaphragm 55, and *rounded by an annularspace lf bounded hy the exterior surface of the cone and the interiorsurface of the end of the n'iouthpiece.

IVith the arrangement of perforated partition 9 described above, it isfound that the sound waves entering the aperture 8 and passing throughthe perfor-ations 10 pass along the wall of the mouthpiece to the cone12, whence they issue to act upon the diaphragm 3, and that such surfaceconduction of the sound waves results in abetter transniission of thesound waves to the diaphragm with a better action of the waves on thediaphragm and corresponding vgreater distinctness in reproduction of thesounds. The cone 12 condenses or concentrates the sound waves on thediaphragm and the surrounding annular space 13 serves as an expansionchamber for the sound waves rebounding from the diaphragm, therebypreventing such waves from interfering with the waves issuing from thecone, which also results in a better action of the sound waves on thediaphragm and greater distinctness in reproduction.v p

Instead of the cone 12 lying within the end of the concentratormouthpiece 2, it may be made integral with said end, as shown in Fig. 8,or may extend therebeyond, as shown in Fig. 6, in whichv cases theannular space 13 will, as shown in Fig. 8, be formed between theexterior surface of the cone and the interior surface of the ferrule 11or equivalent into which the end of the mouthpiece is iitted.

In Fig. 3 the concentrator cap and perforated partition are shownapplied to the standard mouthpiece in which the exit is in line with theentrance. The arrangement of the cap and perforated partition and therelative proportions of the areas of the aperture 8 partition 9 andperforatiors 10 are preferably as above described. As the moisture ofthe breath will condense and deposit on the partition 9 the grid 14usually provided at the inner end of mouthpieces of this type may bedispensed with without fear of said moisture reaching and affecting thediaphragm. The inner or exit end of this form of concentrator mouthpiecemay also be fitted with a cone lying within the end as in Fig. 1, orprojecting therebeyond as in Fig. 6, or be formed with a tapered orconed end as in Fig. 8 so that when the mouthpiece is fitted to thecasing of the instrunient the annular space 13, Fig. 1, results.

Instead of the perforated partition 9 being flat as illustrated in Figs.1 and 3 the face thereof next the aperture 8 may be convex as in Fig. 4,or concave as in Figf.

The sound wave concentrator provided with a perforated partition asabove described may be used by' the partially deaf, and in such case thedevice preferably takes the form of the concentrator mouthpiece shown inFig. 1, and has its end provided with a projecting cone as in Fig. 6, ortapered or coned as in Fig. 8 for insertion into the ear, or has itssaid end provided with a flange 15 or the like, as shown in Fig. 8 forholding against the ear.

What I claim and desire to secure by Letters Patent is 1. A sound waveconcentralor comprising a mouth piece having a constricted opening forthe entrance of sound waves and walls, Iii-st divergent from the openingand then convergent towardsl the exit end, a partition having asubstantially flat surface arranged across the interior of the mouthpiece at the junction of the divergent and convergent walls, saidpartition being imperforate at its central portion and apertured at itsouter annular portion, the area of said opening at the entrance endbeing approximately one-fourth the area between the walls at the'junction of the divergent and convergent walls.

2. A sound wave concentrator comprising a mouth piece having aconstricted opening for the entrance of sound waves and walls, firstdiver-gent from the opening and then convergent towards the exit end, apartition arranged across the interior of the mouth piece at the`junction of the divergent and convergent walls, said partition beingimperforate at its central portion and apertured at its outer annularportion, the distance between the constrictcd opening and the partitionbeing approxin'iately onefourth the diameter of the latter.

3. A sound wave concentrator comprising a mouth piece having aconstricted opening for the entrance of sound waves and walls, firstdivergent from the opening and then convergent towards the exit end, apart-i- 4tion arranged across the interior of the mouth piece at thejunction of the divergent and convergent walls, said partition beingimperforate at its central portion and apertured at its outer annularportion, the divergent wall being cur-ved with a radius approximatelyequal .to the distance from the constricted opening to the partition. u

4. A sound wave concentrator comprising a mouth piece having aconstricted opening for the entra-nce of sound waves and walls, firstdivergent from the opening and then convergent towards the exit end, apartition arranged across the interior of the mouth piece at thejunction of thcrdivergent and convergent walls, said partition beingimperforate at its central portion and apertured at its outer annularportion, the area of said opening at the entrance end beingapproximately one-fourth the area between the walls at the junction ofthe divergent and convergent walls, the distance between the constrictedopening and the partition tif) l:eingapproximately onatourth thediameter of the latter.

5. A sound wave concentrator comprising a mouth piece having aconstricted Opening 'for he entrance of sound waves and walls, trstdivergent from the opening and then convergent towards the exit end, apartition arranged across the interior ot the mouth piece at thejunction of the divergent and convergent walls, said partition beinginipertorate at its central portion and apertured at its outer annularportion, the area 01'. said opening at the entrance end beingapproximately one-fourth the area between the walls at the junction otthe divergent and convergent walls, the divergent wall being curved witha radius approximately equal to the distance or' the constricted openingto the partition.

(i. A sound wave concentntor comprising a mouth piece raving aconstricted opening for the entrance of sound waves and walls, firstdivergent from the opening and then convergent towards the exit end, apartition arranged across the interior ot the mouth piece at thejunction of the divergent and convergent walls, said partition beinginiperforate at its central portion and apertured at its outer annularportion, the area ot said opening at the entrance ond being aparoiziinately one-fourth the area between the walls at the junction ofthe divergent and convergent walls, the distance between the constrictedopening and the partition being approximately one-fourth the diameter otthe latter, the divergent wall being curved with a radius approximatelyequal to the distance of the constricted opening to the partition.

7. A sound wave concentrator comprising a mouth piece having aconstricted opening for the entrance ot sound waves and walls, iirstdivergent from the opening and then convergent towards the exit end, apartition arranged across the interior of the mouth piece at thejunction of the divergent and convergent walls, said partition beingimperforate at its central portion and apertured at its outer annularportion, the collective area of the apertures in the partition being notless than the area of the constricted opening.

S, A sound wave concentrator comprising a mouth piece having aconstricted opening ttor the entrance of sound waves and walls, iirstdivergent lirom the opening and then convergent towards the exit end, apartition arranged across the interior oit' the month piece at thejunction of the divergent and convergent walls, said partition beingiinperiforate at its central portion and aperlured at its outer annularportion, the collective area ot the apertures in the partition being notless than the area o't the constricted opening, the area of said openingat the entrance end being approximately onetourth the area between thewalls at the junction et the divergent and convergent walls.

tl. A sound wave concentrator comprising a mouth piece having aconstricted opening lor the entrance oit sound waves and walls, irstdivergent from the opening and then convergent towards the exit end, apartition arranged across the interior ot the mouth piece at thejunction 01"' the divergent and convergent walls, said partition beingimperforate at its central portion and apertured at its outer annularportion, the collective area of the apertures in the partition being notless than the area of the constricted opening, the distance between theconstrioted opening and the partition being approximately one-fourth thediameter of the latter.

l0. A sound wave concentrator co1npris ing a mouth piece having aconstricted opening for the entrance ot' sound waves and walls, iirstdivergent from the opening and then convergent towards the exit end, apartition arranged across the interior of the mouth piece at thejunction of the divergent and convergent walls, said partition beingimperforate at its central portion and apertured at its outer annularportion, the collective area of the apertures in the partition being notless than the area of the constricted opening, the divergent wall beingcurved with a radius approximately equal to the distance of theconstricted opening to the partition.

In witness whereof I have hereunto set my hand.

ALEXANDER MAR-R.

